E. Masuyer

Recent estimates of global cancer incidence and survival were used to update previous figures of limited duration prevalence to the year 2008. The number of patients with cancer diagnosed between 2004 and 2008 who were still alive at the end of 2008 in the adult population is described by world region, country and the human development index. The 5-year global cancer prevalence is estimated to be 28.8 million in 2008. Close to half of the prevalence burden is in areas of very high human development that comprise only one-sixth of the world's population. Breast cancer continues to be the most prevalent cancer in the vast majority of countries globally; cervix cancer is the most prevalent cancer in much of Sub-Saharan Africa and Southern Asia and prostate cancer dominates in North America, Oceania and Northern and Western Europe. Stomach cancer is the most prevalent cancer in Eastern Asia (including China); oral cancer ranks as the most prevalent cancer in Indian men and Kaposi sarcoma has the highest 5-year prevalence among men in 11 countries in Sub-Saharan Africa. The methods used to estimate point prevalence appears to give reasonable results at the global level. The figures highlight the need for long-term care targeted at managing patients with certain very frequently diagnosed cancer forms. To be of greater relevance to cancer planning, the estimation of other time-based measures of global prevalence is warranted.

Cholangiocarcinoma is relatively rare, but high incidence rates have been reported in Eastern Asia, especially in Thailand. The etiology of this cancer of the bile ducts appears to be mostly due to specific infectious agents. In 2009, infections with the liver flukes, Clonorchis sinensis or Opistorchis viverrini, were both classified as carcinogenic to humans by the International Agency for Research on Cancer for cholangiocarcinoma. In addition, a possible association between chronic infection with hepatitis B and C viruses and cholangiocarcinoma was also noted. The meta-analysis of published literature revealed the summary relative risks of infection with liver fluke (both Opistorchis viverrini and Clonorchis sinensis), hepatitis B virus, and hepatitis C virus to be 4.8 (95% confidence interval [95% CI]: 2.8-8.4), 2.6 (95% CI: 1.5-4.6), and 1.8 (95% CI: 1.4-2.4), respectively - liver fluke infection being the strongest risk factor for cholangiocarcinoma. Countries where human liver fluke infection is endemic include China, Korea, Vietnam, Laos, and Cambodia. The number of infected persons with Clonorchis sinensis in China has been estimated at 12.5 million with considerable variations among different regions. A significant regional variation in Opistorchis viverrini prevalence was also noted in Thailand (average 9.6% or 6 million people). The implementation of a more intensive preventive and therapeutic program for liver fluke infection may reduce incidence rates of cholangiocarcinoma in endemic areas. Recently, advances have been made in the diagnosis and management of cholangiocarcinoma. Although progress on cholangiocarcinoma prevention and treatment has been steady, more studies related to classification and risk factors will be helpful to develop an advanced strategy to cure and prevent cholangiocarcinoma.

Head and neck cancers (ICD-9 categories 140-149 and 161) are common in several regions of the world where tobacco use and alcohol consumption is high. The age standardized incidence rate of head and neck cancer (around 1990) in males exceeds 30/100, 000 in regions of France, Hong Kong, the Indian sub-continent, Central and Eastern Europe, Spain, Italy, Brazil, and among US blacks. High rates (> 10/100,000) in females are found in the Indian sub-continent, Hong Kong and Philippines. The highest incidence rate reported in males is 63.58 (France, Bas-Rhin) and in females 15.97 (India, Madras). The variation in incidence of cancers by subsite of head and neck is mostly related to the relative distribution of major risk factors such as tobacco or betel quid chewing, cigarette or bidi smoking, and alcohol consumption. Some degree of misclassification by subsites is a clear possibility in view of the close proximity of the anatomical subsites. While mouth and tongue cancers are more common in the Indian sub-continent, nasopharyngeal cancer is more common in Hong Kong; pharyngeal and/or laryngeal cancers are more common in other populations. While the overall incidence rates show a declining trend in both sexes in India, Hong Kong, Brazil and US whites, an increasing trend is observed in most other populations, particularly in Central and Eastern Europe, Scandinavia, Canada, Japan and Australia. The overall trends are a reflection of underlying trends in cancers of major subsites which seem to be related to the changing prevalence of risk factors. The five year relative survival varies from 20-90% depending upon the subsite of origin and the clinical extent of disease. While primary prevention is the potential strategy for long term disease control, early detection and treatment may have limited potential to improve mortality in the short term.

Tobacco smoking is accepted as a major cause of cancers of the lung, larynx, oral cavity and pharynx, oesophagus, pancreas, kidney and bladder. The proportions of these cancers that are due to smoking were estimated for the year 1985 for 24 areas of the world. Fifteen percent--1.1 million new cases per year--of all cancer cases are attributed to cigarette smoking, 25% in men and 4% in women. In developed countries, the tobacco burden is estimated at 16% of all annual incident cases. In developing countries, the corresponding figure is 10%. In total, 85% of the 676,000 cases of lung cancer in men are attributable to tobacco smoking. The highest attributable fractions (AF: 90-93%) are estimated in areas where the habit of cigarette smoking in men has been longest established: North America, Europe, Australia/New Zealand and the former USSR. Among the other 6 cancer sites considered in this analysis, those with the largest fractions of tobacco-related cases are the larynx, mouth and pharynx (excluding nasopharynx) and oesophagus. In regions where males have smoked for several decades, 30 to 40% of all cancers in this sex are attributable to tobacco. Unless tobacco-control efforts in developing countries are strengthened, the massive rise in cigarette consumption over the last few decades will produce a comparable rise in cancer in these countries within the next 20 to 30 years.